1. Field of the Invention
The invention relates to a valve apparatus which may be utilized in a fluid transmission conduit of a subterranean well to isolate fluid flow passing therethrough.
2. Description of the Prior Art
It is frequently necessary to isolate the flow of fluids within a fluid transmission conduit, such as a tubing string in a subterranean well. The prior art is familiar with many varied designs of the valves, particularly "safety" valves that utilize a ball having a flow passageway therethrough as the valve head. Such valves have been found to be particularly reliable in subterranean well applications.
One type ball valve utilizing a cam action to manipulate the valve is disclosed in U.S. Pat. No. 4,210,207. That valve apparatus was responsive to rotational manipulation of the fluid transmission conduit which permitted the valve to be activated before and/or after the setting or release of another tool, such as a packer, bridge plug or the like. Other prior art ball valves have utilized camway slots defined on the exterior of or relative to the seat of the valve in response to hydraulic activation through the incorporation of piston means. Valves incorporating other actuating means are also known in the art.
Prior art mechanical ball valves may be difficult to activate in the presence of a pressure differential existing across the valve. Such pressure differentials may result from the presence of excessive pressure existing either above or below the ball valve apparatus. Mechanically activated valves in the presence of large pressure differentials often resist mechanical rotation. The present invention provides a valve apparatus which not only enables rotational manipulation and pivoting of the ball valve utilizing less torque than previously required, but also provides continuous seals to isolate pressure differentials when the valve is in the closed position.